Producing (X)HTML files can be done with a wide variety of software, and in general web browser are very forgiving of errors in HTML code. In most cases it would still be unwise to use office applications for creating (X)HTML documents. Although some office software applications are now quite good at generating clean (uncluttered) code, there are always some mistakes. Never under any circumstances use Microsoft Word's "Save as HTML function". The code that will be produced is full of non-standard, Microsoft-specific extensions, and the files it produces are very large.

The advantage of (X)HTML is that it can always be read with your eye, whether you have a suitable browser or not. For example, the title of an HTML page (if you look at the code of the file) is surrounded by <title> and </title> so it looks like this:

<title>
A page about me
</title>

This makes (X)HTML ideal for storing text files with structure. You are however limited by your ability to create (X)HTML files and (X)HTML's limitations on formatting

Recommendation

Set the DTD and (X)HTML flavour your software uses before starting a new file